Multiple tap device for transformers



Feb. 24, 1970 D. J. CORRIGALL MULTIPLE TAP DEVICE FOR TRANSFORMERS Filed April 19, 1968 INVENTOR DON J. CORRlGALL ATTORNEYS United States Patent O ice 3,497,848 MULTIPLE TAP DEVICE FOR TRANSFORMERS Don .I. Corrigall, Appleton, Wis. S4911 Filed Apr. 19, 1968, Ser. No. 722,712 Int. Cl. H01f 21/12 US. Cl. 336-150 2 Claims ABSTRACT OF THE DISCLOSURE An arrangement for tapping a multiturn conductor wound on a core such as used for arc welding transformers in order to make an adjustable voltage transformer includes a coil with multiple turns wound in a package on a core with selected ones of the turns wound also over a grooved insulator block extending axially of the core so that a portion extends outwardly of the package. Conductive clips are positioned in the grooves so as to be affixed to the insulator blocks and under the conductors so as to be in conductive contact therewith. The clips extend outwardly. A rotary connector member includes a contact assembly with connector arms for engaging the clips as the connector assembly is rotated and thereby selecting desired turns of the coil for a connection.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to multiple tap devices for tapping into a coil of wire at selected points along the length thereof.

Prior art The acceptable prior art method of making adjustable voltage transformers at the present time is by either using brushes which are slidable along a carefully prepared winding or by physically bringing wires out of the transformer coil at the desired tap points.

The former method, above, requires that the transformer be carefully wound with the individual turns of the conductor lying in a very uniform manner with respect to each other. The turns of the conductor are then cleaned of any insulation and smoothed to eliminate any unevenness. A brush assembly having a slider operated by a lead screw is then constructed and arranged relative to the transformer coil so that the brushes which are similar to carbon electric motor brushes make a sliding and continuous contact along the transformer winding. While this form of variable voltage transformer is very good in that a continuous control is obtained, such an arrangement has several disadvantages. The brushes usually represent a high resistance and there is appreciable heat which places limitations on the capacity as well as producing a loss of efliciency. This type of construction must also accommodate for the possibility of circulating current when the brushes are in contact with two turns of the winding simultaneously. The whole process is quite critical and a great deal of care is needed in the construction of the coil,

The second method of making a tapped transformer is to bring out taps from the coil at the desired location. This involves much work and wiring if a selector switch is to be used. When making many taps, the procedure become costly. It is common practice with heavy currents, such as in welding transformers, to braze the transformer taps to the winding conductor. A second way is to make multiple windings and externally connect these to produce the equivalent of tap points. In either case, a considerable expenditure of time and money is required.

SUMMARY OF THE INVENTION The multiple tap device for transformers, according 3,497,848 Patented Feb. 24, 1970 to the present invention, provides an easy and economical manner of making taps for a transformer coil and at the same time provides simple and efficient tap changing means.

The present invention is especially suited to handling high currents and applications where a large number of consecutive or nearly consecutive taps are required, such as in the welding art.

The present inventon provides a coil having a plurality of taps without having to treat the turns of the coil in any special manner or to braze taps at specific locations to the winding conductor. The taps, according to the present invention, are formed concurrently with the wind ing of the coil and are sufficiently isolated from each other so that successive taps can be made without overlapping.

Other features of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose by way of example, the principles of the invention and the best mode which has been contemplated of applying those principles.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a side elevational view, partly in section, showing the multiple tap device for a transformer;

FIGURE 2 is a sectional view along the line 22 in FIGURE 1 and FIGURE 3 is a sectional view along the line 3-3 in FIGURE 2.

DETAILED DESCRIPTION OF THE INVENTION A transformer coil 10 having a plurality of turns is wound about a core member 12. An elongated insulating block member 14 is provided with a plurality of notches 16 in the upper surface thereof in each of which is mounted a J-shaped contact clip 18. The clips 18 may be molded or pressed into their respective notches 16 or may be merely secured thereto by rivets, screws or the like. Each of the clips 18 is constructed from a hard conductive material such as beryllium copper and may be provided with dimples or other suitable projections 20 in the bight portion thereof to bite into a wire for good contact.

In constructing the coil 10 the block 14 is placed in position on a winding machine and selected winding turns 22 of the coil 10 on which a tap is to be made are then brought over the block 14 and positioned over a specific clip 18 in the block. If the selected turn of wire 22 is insulated, it is best to strip the insulation from the wire and thereafter press or dirve the wire into the bight of the J-shaped clip 18. Each consecutive tap on the transformer winding is made in the same manner.

After the coil 10 is completely wound about the core 12 and the block 14, a pair of shaft supporting end plates 24 and 26 are secured to the ends of the insulating block 14 by any suitable means such as screws 28 or the like, A shaft 30 is rotatably journaled through the openings in the plates 24 and 26 and is disposed parallel to the insulating block 14 and the axis of the coil 12. A plurality of contact assemblies, one of which is generally indicated at 32 in FIGURE 1, are secured to the shaft 30 at spaced locations along the length thereof. The number of contact assemblies 32 correspond in number to the number of contact clips 18 secured to the insulating block 14. Each assembly 32 is comprised of a hub 34 and and a pair of resilient contact arms 36 and 38 secured thereto. The resilient contact arms 36 and 38 of each assembly extend radially outwardly from the shaft and each assembly is angularly spaced from each and every other contact assembly so that only one contact assembly 32 will contact a clip 18 at a time. In the present example, six contact assemblies 32 are mounted on the shaft 30 and are angularly spaced from the adjacent contact assembly by an angle of 60 in a progressive relationship so that upon rotation of the shaft 30 each contact assembly 32 will engage its respective clip 18 in sequence from left to right as viewed in FIGURE 1. Each contact arm 36 and 38 is provided with a projection or dimple 40 to aid in making a positive contact with the clip 18.

An indexing plate 42 may be secured to the shaft 30 adjacent the support plate 24. A spring bias ball detent assembly comprised of a ball 44, a spring 46 and a socket member 48 is mounted in the support plate 24. The ball 44 is biased into engagement with the indexing plate 42 for locking engagement with detents 50 arranged in a circle on said plate. Each detent 50 is positioned angularly relative to the shaft 30 corresponding to the angular position of a respective contact assembly 32.

A handle 52 is secured to one end of the shaft 30 to provide for manual rotation of the shaft 30 to sequentially engage the contact assemblies 32 with their respective contact clips 18. A suitably programmed power driven arrangement could also be substituted for the handle 52 to automatically index the shaft 30 to the predetermined connection. A common switch terminal 54 may be connected to the end plate 26 in common conducting relation to each of the contact assemblies 32 through their respective hubs 34 and the common shaft 30.

Thus, it is seen that the method of making the present tapped transformer is very fast and eflicient. On large coils of heavy conductors, it is nearly as fast as winding a coil alone. The clips 18 provide a heat sink for the windings and there are no circulating currents since each position can be made non-shorting. There is no special coil preparation necessary such as smoothing and polishing and the contact elements 36, 38 and 18 can all be of low resistance, making the tapping arrangement efl'icient and capable of high currents. No leads come out of the transformer which require a multitude of connec tions at each tap. There are many uses for a multiple tap arrangement such as that shown in the present application, including tapped reactors, tapped stabilizers, tapped Slope reactors, tapped transformers, battery chargers and the like.

What is claimed is:

1. A multiple tap arrangement for tapping a multiturn coil conductor wound on a core such as used as in arc welding transformer by tapping selected turns of the coil to provide a variable Voltage transformer, the arrangement comprising: a coil having multiple turns wound in a package on a core with selected turns also wound over an insulator block extending axially of the coil so that a portion of each such selected turn protrudes from the outline of the package along one surface thereof, a plurality of conductive clips, each clip affixed to the insulator block and in conductive contact with the protruding portion of each selected turn, a connector member mounted adjacent the package and including a contact assembly rotatably mounted on an axis parallel to the coil, axially spaced connector arms extending from the rotatable contact assembly and extending outwardly, the rotatable contact assembly being radially outward of the coil package at the protruding surface portion thereof so that the connector arms may selectively contact and electrically connect the conductive clips on rotation of the contact assembly.

2. A multiple tap arrangement as in claim 1 wherein the insulating block has transverse grooves therein for positioning the selected turns, and the conductive clips are positioned in the transverse grooves with a portion of each clip underneath the corresponding protruding turn and another portion of each conductive clip extending outwardly of the coil radially toward the contact assembly.

' References Cited UNITED STATES PATENTS 1,524,976 2/1925 Kautz 336- XR 1,763,278 6/1930 Trogner 336-l37 1,818,363 8/1931 Trogner a. 336150 XR 1,840,391 1/1932 Gebhard 336-150 XR 2,439,827 4/1948 Sterenbuch et a1. 33'6--150 XR 3,365,686 1/1968 Petersen 336-150 THOMAS J. KOZMA, Primary Examiner U.S. Cl. X-.R. 338-485 

